Herbicides are widely used to control weed growth in growing crop plants. Unchecked weed growth is detrimental to the crop plant because weeds compete with crop plants for light, water and various nutrients. This can result in lower crop yields as well as poorer crop quality. The presence of weeds in a growing crop also interferes with the cultivation and harvesting of the crop plant. Among the commercially available herbicides, thiocarbamates and acetanilides have proven to be effective in controlling various weed pests. Unfortunately, thiocarbamate and acetanilide herbicides can also cause serious injury to some crop plants at application rates necessary to stunt or kill weeds. A compound or composition which protects the crop plant from the action of the herbicide, without reducing the herbicidal effectiveness against the weed to be controlled, would be beneficial.
Compounds which are useful in reducing or eliminating crop injury are variously referred to by those skilled in the art as antidotes, safeners or antagonistic agents. It has been found that certain 2-imino derivatives of 1,3-dithiolane, 1,3-dithiole, 1,3-dithiane, 1,3-dithietane and 1,3-oxathiole are effective safening agents. Certain of these compounds are known in the art; the following patents are representative of the art in this area.
U.S. Pat. No. 3,449,365 discloses 2-imino-4-alkalidene-1,3-dithiolanes and teaches that said compounds are useful as insecticides, acaricides and nematocides. U.S. Pat. No. 3,449,366 discloses 2-amino-4,5-substituted-1,3-dithioles which are useful as insecticides. U.S. Pat. No. 3,389,148 discloses processes for preparing substituted 1,3-dithioles, 1,3-dithianes, 1,3-dithiolanes and the salts thereof which are intermediates in the preparation of phosphorylated imino compounds. U.S. Pat. No. 3,189,429 and 3,139,439 disclose the preparation and herbicidal use of the halide salts of 2-dialkylamino-1,3-dithiolane derivatives. British Pat. No. 1,367,862 discloses substituted phenyl-2-imino-1,3-dithietanes which are chemosterilants of adult female Ixodides. U.S. Pat. No. 4,025,532 discloses 2-(o-tolyl)imino-1,3-dithioles which are ixodicides. None of the above patents teach or suggest that the substituted 2-imino-1,3-dithio and 1,3-oxathio heterocyclic compounds of the present invention would be useful as herbicidal antidotes.